1. Field of the Invention
The present invention relates to a sheet feeding apparatus and an image forming apparatus including the sheet feeding apparatus.
2. Description of the Related Art
In U.S. Patent Application Publication No. 2009/0152801 A1, a torque limiter is provided on one side of a separation roller shaft, and a D-like cut portion is formed on one end of a torque limiter shaft. The D-like cut portion formed on one end of the torque limiter shaft is supported by the separation roller, and the other end of the torque limiter shaft is supported by a bearing. In a case of this configuration, when the separation roller and a feeding roller rotate, a torque is applied to the D-like cut portion due to the function of the torque limiter and a twisting occurs in the separation roller. Thus, a pressure by which the separation roller is pressed against the feeding roller may become non-uniform in an axial direction of the separation roller. This phenomenon has influence on accuracy of a sheet conveyance.
In addition, a configuration of forming the D-like cut portion on both ends of the torque limiter shaft may be also considered. In such case, since a separation torque is applied to both ends of the shaft, it may theoretically be an effective configuration in that the influence of the separation torque is equally distributed in the right and left of the separation roller.
However, it is extremely difficult to assure a stable effect in an actual apparatus. The reason is that the assurance of a dimensional relation capable of equally distributing the separation torque in the right and left is practically unachievable due to variation in machining accuracy. Examples of factors causing the variation in machining accuracy include dimensional differences between the D-like cut portions provided on both ends of the separation roller shaft (corresponding to the torque limiter shaft described above), dimensional differences between shapes of holders engaging with the D-like cut portions, width dimensions of a bearing for supporting the separation roller shaft, width dimensions of a guide portion for slidingly regulating the bearing, and rigidity of each part or shapes. There are many factors that cause the difference between the right and the left, and thus it is not realistic to perfectly manage these all. Therefore, the above problems are not solved only by providing the D-like cut portion on both ends of the separation roller shaft.